On 31 May the vessel came under fire from shore batteries off Bray and sustained 15 casualties. Dechaineux received a minor wound to his forehead and a piece of shrapnel tore the back of his trousers In a letter to his wife he remarked "I am very grateful that the ship was heading away from the gunfire, rather than towards it!” On 1 June another 427 men were brought back to Dover. On 3 June the destroyer was directed to take part in Operation OK, which sank blockships, to provide a temporary wharfage point, in Dunkirk Harbour. Vivacious safely brought the crews of these ships back across the Channel. Altogether the destroyer brought out a total of 1,649 passengers from Dunkirk during five voyages. The evacuation lasted nine days, and safely brought hundreds of thousands of men back to Britain. Four years later, many would return for the D-Day landings. Dechaineux had proved his worth during his baptism of fire, not only by commanding the ship through battle, but also through the effective leadership of his men. He was destined for greater things. On 25 September 1940 he was given command of the brand new Hunt-class escort destroyer, HMS Eglington. After working up to satisfactory operational capability in Scapa Flow – where the ship and her captain were assessed by RN experts – the last months of the year were spent on North Sea convoy escort duties, as was 1941, although on 4 October the ship carried out a brief search for a German destroyer reported minelaying off South Foreland. In 1941, he was awarded the Distinguished Service Cross. Dechaineux returned to Australia later in 1941, as Director of Operations at the Navy Office in Melbourne. In June 1943, following the outbreak of war with Japan, he was given command of the tactical (destroyer) component of RAN-US Navy Task Force 74. From his immediate command, HMAS Warramunga, Dechaineux commanded operations in waters around Australia and New Guinea, including support for amphibious landings, such as those in the Admiralty Islands. He was promoted to Captain on 31 December 1943. On 9 March 1944, Dechaineux was given command of the heavy cruiser HMAS Australia, the flagship of both the RAN and Task Force 74, under the overall force commander Commodore John Collins. The Australia supported Allied landings at Hollandia in Dutch New Guinea and on the islands of Biak, Noemfoor and Morotai.